Synthesis of certain tetrahydroacridine derivatives of anticipated medicinal value

Article abstract of DOI:10.1007/s11164-012-0857-6

This study aims at the synthesis and evaluation of the chemotherapeutic activity of a number of 9-substituted tetrahydroacridine derivatives. The starting material, acridine hydrazide, could be prepared through the interaction between cyclohexanone and anthranilic acid, then chlorination of the product, then condensation of the last compound with hydrazine hydrate. The structures of the new compounds were established by IR, ¹H NMR, MS spectra, and elemental analysis in certain cases. Antitumor activities as a trial to obtain more effective and less toxic agents were evaluated. The antitumor activity results indicated that the selected tetrahydroacridine derivatives showed antitumor activity against the liver cancer (HEPG2) tumor cell line tested, but with varying intensities in comparison to the known anticancer drugs, 5-fluorouracil and doxorubicin. It was found that compound VIb was the most active and induced a marked growth inhibition (0.694 μg/ml concentration) in a dose-dependent manner against liver cancer (HEPG2), while compound XVIIIa was second in regards to the growth inhibition activity (2.97 μg/ml concentration).

Full text of DOI:10.1007/s11164-012-0857-6

Res Chem Intermed
DOI 10.1007/s11164-012-0857-6
Synthesis of certain tetrahydroacridine derivatives
of anticipated medicinal value
•
Omar A. Fathhalla Mosaad S. Mohamed
•
•
Madeha A. Farag Rehab Sayed Ahmed Ismail
Received: 6 June 2012 / Accepted: 5 October 2012
Ó Springer Science+Business Media Dordrecht 2012
Abstract This study aims at the synthesis and evaluation of the chemotherapeutic
activity of a number of 9-substituted tetrahydroacridine derivatives. The starting
material, acridine hydrazide, could be prepared through the interaction between
cyclohexanone and anthranilic acid, then chlorination of the product, then con-
densation of the last compound with hydrazine hydrate. The structures of the new
compounds were established by IR, 1H NMR, MS spectra, and elemental analysis in
certain cases. Antitumor activities as a trial to obtain more effective and less toxic
agents were evaluated. The antitumor activity results indicated that the selected
tetrahydroacridine derivatives showed antitumor activity against the liver cancer
(HEPG2) tumor cell line tested, but with varying intensities in comparison to the
known anticancer drugs, 5-fluorouracil and doxorubicin. It was found that com-
pound VIb was the most active and induced a marked growth inhibition (0.694
lg/ml concentration) in a dose-dependent manner against liver cancer (HEPG2),
while compound XVIIIa was second in regards to the growth inhibition activity
(2.97 lg/ml concentration).
Keywords 9-Substituted tetrahydroacridine derivatives ꢀ The antitumor activity
against the liver cancer (HEPG2) tumor cell line
O. A. Fathhalla (&) ꢀ R. S. A. Ismail
Medicinal Chemistry Department, National Research Centre, Dokki, Cairo, Egypt
e-mail: omarfathalla@yahoo.com
M. S. Mohamed ꢀ R. S. A. Ismail
Organic Chemistry Department, Faculty of Pharmacy, Helwan University, Cairo, Egypt
M. A. Farag ꢀ R. S. A. Ismail
Pharmaceutical Chemistry Department, Faculty of Pharmacy, Helwan University, Cairo, Egypt
123

O. A. Fathhalla et al.
Introduction
Acridine and 1,2,3,4-tetrahydroacridine derivatives, well known as DNA interca-
lates, have been widely studied from a variety of viewpoints, such as synthesis
[1, 2], physicochemical properties [3, 4], structural requirements [5], and biological
activities [6, 7]. Due to their polycyclic planar structure, acridine and its derivatives
intercalate within DNA and RNA by forming hydrogen bonds and stacking between
base pairs, resulting in DNA cross links and strand breaks [8]. A variety of natural
and synthetic acridine derivatives have also been tested for antimalarial [9],
antiinflammatory [10, 11], and analgesic [12] activities, and some of them have
been approved for chemotherapy. The 1,2,4-triazole nucleus has been incorporated
into a wide variety of therapeutically important agents. Ribavirin (antiviral),
letrozole, and anastrozole (antitumor) are some examples of drugs containing the
1,2,4-triazole moiety [13–17]. 1,3,4-Thiadiazole derivatives are another important
class of heterocycles due to their biological activities. The only commercially
available 1,3,4-thiadiazole drugs are desaglybuzole, acetazolamide, and furidiazine
[18–20]. Moreover, 1,3-thiazoles recently found application in drug development
for the treatment of hypertension [21], schizophrenia [22], HIV infections [23], and
as new inhibitors of bacterial DNA gyrase B [24]. Furthermore, 1,3-thiazine
derivatives have antibacterial [25] and cannabinoid receptor agonist [26] activity.
In view of the above-mentioned findings and in continuation of our efforts to
identify new candidates that may be of value in designing new and potent
antimicrobial agents [27–29], we decided, in the present work, to synthesize new
1,3-thiazole, 1,3,4-thiadiazole, 1,2,4-triazole, and 1,3-thiazine derivatives bearing
acridine and 1,2,3,4-tetrahydroacridine moieties in order to investigate their
antimicrobial activities.
Materials and methods
All melting points were uncorrected and measured using Electro-thermal IA 9100
apparatus (Shimadzu, Japan). Microanalytical data were obtained by Vario El-Mentar
apparatus (Shimadzu, Japan), at the National Research Centre (NRC), Cairo, Egypt. The
found values were within 0.4 % of the theoretical values. IR spectra (KBr) were
recorded on a Perkin-Elmer 1650 spectrophotometer, at the NRC. 1H NMR and 13C NMR
spectra were determined on a Varian Mercury 300 MHz spectrometer (Varian, UK) and
the chemical shifts were expressed in d ppm relative to TMS as an internal reference
(Faculty of Science, Cairo University, Egypt). Mass spectra were recorded at 70 eV using
an EI Ms-QP 1000 EX instrument (Shimadzu, Japan), at the NRC. Follow up of the
reactions and checking the purity of the compounds were was done by TLC on silica gel-
protected glass plates and the spots were detected by exposure to a UV lamp at k = 254.
Method for preparation of 1,2,3,4-tetrahydroacridine (I)
A mixture of cyclohexanone (10 ml) and anthranilic acid (10 g) was placed in a
flask provided by a still head and a condenser in a sand bath held at 120 °C for half
123

Synthesis of certain tetrahydroacridine derivatives
an hour. The still head was then lagged and the temperature of the sand bath raised
in half an hour to 160 °C, when vigorous boiling set in.
In the next half hour, the temperature was raised to 230 °C, when the content of
the flask swelled and solidified. Heating was continued for a further half an hour at
230 °C. Then, the flask was cooled and the contents were grounded with benzene
75 ml. The suspension was refluxed for half an hour, filtered whilst hot, and the
residue washed with more benzene to remove the excess aniline and cyclohexanone,
washed with petroleum ether, filtered, and dried.
Method for preparation of 9-chloro-1,2,3,4-tetrahydroacridine (II)
A mixture of tetrahydroacridine (19.8 g, 0.1 mol) and 17 ml phosphoryl chloride
was heated in a sand bath at 125–130 °C for an hour. The reaction mixture was then
cooled, mixed thoroughly with benzene (50 ml), and poured onto 5 N sodium
hydroxide (150 ml) using a mechanical stirrer.
After 10 min, it was confirmed that the liquid was still alkaline, and the aqueous
layer was extracted successively three times with benzene (each with 20 ml). The
combined benzene extracts were dried over sodium sulfate, filtered, dried, and
crystallized from acetone.
Method for preparation of 9-substituted amino-1,2,3,4-tetrahydroacridine (IIIa, b)
9-hydrazide-1,2,3,4-tetrahydroacridine (IIIa)
A mixture of II (21 g) and (21 ml) hydrazine hydrate was dissolved in (70 ml)
n-butanol as the solvent, and then the reaction mixture was refluxed for 24 h. The
formed precipitate after cooling was filtered off, dried with air suction, and then
crystallized from methanol to give 9-hyrazino-1,2,3,4-tetrahydroacridine HCl. Pale
yellow powder with m.p. 273–275 °C and yield 51 %. IR spectrum (K Br, cm-1):
3344 (NH), 3335, 3065 (C–H aromatic); 1H NMR spectrum (DMSO-d6, ppm): 1.85
(mm, 4H, 2CH2), 2.30 (t, 2H, CH2), 3.3 (t, 2H, CH2), 7.2–8.7 (m, 4H, C–H
aromatic), 5.8, 9.1, 11.1 (s, 3H, NH, NH2 exchangeable with D2O); 13C NMR
(DMSO d6): d 20.6, 22.7, 22.8, 31.4, 115.6, 119.5, 119.9, 124.4, 128.2, 128.3,
128.4, 145.4, 147.6, 164.2. Analysis for C13H15N3: required: C, 73.21; H, 7.09; N,
19.70; found: C, 73.19; H, 7.07; N, 19.68.
2-(1,2,3,4-tetrahydroacridin-9-ylamino)benzoic acid (IIIb)
A mixture of II (1 g) and anthranilic acid (0.7 g) in 20 ml absolute methanol with
1 ml pyridine was refluxed for 24 h. The produced precipitate was filtered off, dried
under air suction, and then crystallized from ethanol. Pale yellow powder with m.p.
125–120 °C and yield 51 %. IR spectrum (K Br, cm-1): 3697 (OH), 3444 (NH),
3335, 3065 (C–H aromatic), 1682 (C=O); 1H NMR spectrum (DMSO-d6, ppm): 1.8
(mm, 4H, 2CH2), 2.5 (t, 2H, CH2), 3.08 (t, 2H, CH2), 6.1–7.9 (m, 8H, C–H
aromatic), 9.3 (s, 1H, NH exchangeable with D2O), 9.85 (b, 1H, OH exchangeable
with D2O); 13C NMR (DMSO d6): d 20.4, 22.6, 22.7, 31.4, 110.3, 115.6, 116.2,
123

O. A. Fathhalla et al.
O
COOH
NH2
+
O
NH
I
l3
C
C
O
P
l5
P
Cl
NHR
RNH2
HCl
N
N
IIIa,b
II
IIIa, R = -NH2
IIIb, R =
COOH
Scheme 1 Structure of compounds I–III
118.7, 119.5, 119.9, 124.4, 128.2, 128.3, 131.1, 134.8, 142.6, 145.4, 146.8, 164.2,
169.4. Analysis for C20H18N2O2: required: C, 75.45; H, 5.70; N, 8.80; found: C,
75.45; H, 5.70; N, 8.80 (Scheme 1).
General method for preparation of 9-arylidenylhydrazon-1,2,3,4-
tetrahydroacridine (IVa–c)
A mixture of IIIa (2.13 g, 0.1 mol) and the appropriate aldehyde (0.1 mol), namely,
4-methylbenzaldehyde, 4-methoxybenzaldehyde, and 3,5-dimethoxybenzaldehyde,
in absolute ethanol (15 ml) was refluxed for 18–24 h. The solvent was evaporated
till it had halved and the solid product after cooling was filtered off, dried with air
suction, and then crystallized from ethanol to give the compounds IVa–c.
(E)-9-(2-(4-methylbenzylidene)hydrazinyl)-1,2,3,4-tetrahydroacridine (IVa)
Crystallized from ethanol to give pale brown powder with m.p. 160–165 °C and
yield 64 %. IR spectrum (KBr, cm-1): 3291 (NH), 3172 (CH, st, aromatic), 1634
1
(C=N); H NMR spectrum (DMSO-d6, ppm): 1.85 (4H, m, 2CH2), 2.30 (2H, t,
CH2), 2.5 (3H, s, C–CH3), 3.3 (2H, t, CH2), 7.4 (s, H, CH=N), 7.2–8.7 (m, 8H, C–H
aromatic), 11.3 (s, H, NH exchangeable with D2O). Analysis for C21H21N3 (315):
required: C, 79.97; H, 6.71; N, 13.32; found: C, 79.95; H, 6.69; N, 13.30.
(E)-9-(2-(4-methoxybenzylidene)hydrazinyl)-1,2,3,4-tetrahydroacridine (IVb)
Crystallized from ethanol to give yellowish brown powder with m.p. 240–243 °C
and yield 52 %. IR spectrum (K Br, cm-1): 3213 (NH), 3117 (CH, st, aromatic),
123

Synthesis of certain tetrahydroacridine derivatives
1
1636 (C=N), 1246–1052 (C–O of phenyl alkyl ether); H NMR spectrum (DMSO-
d6, ppm): 1.80 (4H, m, 2CH2), 2.36 (2H, t, CH2), 3.3 (2H, t, CH2), 3.8 (3H, s,
OCH3), 7.7 (H, s, CH=N), 7.4–8.9 (8H, m, C–H aromatic), 11.1 (H, s, NH
exchangeable with D2O). Analysis for C21H21N3O (331): required: C, 76.11; H,
6.39; N, 12.68; found: C, 76.13; H, 6.49; N, 12.88.
(E)-9-(2-(3,5-dimethoxybenzylidene)hydrazinyl)-1,2,3,4-tetrahydroacridine (IVc)
Crystallized from ethanol to give yellow powder with m.p. 165–166 °C and yield
41 %. IR spectrum (K Br, cm-1): 3194 (NH), 3123 (CH, st, aromatic), 1263–1059
1
(C–O of phenyl alkyl ether); H NMR spectrum (DMSO-d6, ppm): 1.8 (4H, m,
2CH2), 2.4 (2H, t, CH2), 3.25 (2H, t, CH2), 3.81, 3.83 (6H, s, 2OCH3), 7.9 (H,
s, CH=N), 6.6–7.8 (7H, m, C–H aromatic), 11.4 (H, s, NH exchangeable with
D2O). Analysis for C22H23N3O2 (436): required: C, 73.11; H, 6.41; N, 11.63; found:
C, 73.01; H, 6.51; N, 11.33.
Method for preparation of 1,2,3,4-tetrahydroacridin-9-yl(N-(1-
hydrazinovinyl)cyclohexanamine) (V)
A mixture of IIIa (2.1 g, 0.1 mol) and cyclohexyl isothiocyanate (1.28 g, 0.1 mol)
in least amounts in ethyl alcohol (10 ml) was refluxed for 10 h, the solvent was
evaporated, and the precipitate was successively washed with ether and chloroform
and crystallized from ethanol to give product V with m.p. 230–235 °C and yield
100 %. IR spectrum (K Br, cm-1): 3370 (NH), 1633 and 1448.28 (C=C, st,
1
aromatic); H NMR spectrum (DMSO-d6, ppm): 1.1–2 (10H, m, 5 CH2), 1.8 (4H,
m, 2CH2), 2.80 (2H, t, CH2), 3.3 (2H, t, CH2), 7.4–8.7 (4H, m, C–H aromatic,
CH–NH of cyclohexane), 4.3, 9.4, 10.4 (3H, s, 3NH exchangeable with D2O).
Analysis for C20H25N3S (339.1): required: C, 70.76; H, 7.42; N, 12.38; found: C,
70.75; H, 7.44; N, 12.44.
General method for preparation of 1-(1,2,3,4-tetrahydroacridin-9-yl)-3-methyl-
5-substituted pyrazole (VIa, b)
A mixture of IIIa (2.1 g, 0.1 mol) and the appropriate 1,3-dicarbonyl compound
(ethyl acetoacetate, acetylacetone) in absolute ethanol (30 ml) was heated in a water
bath for 7 h. The reaction mixture was allowed to cool, and the solid formed was
filtered off, dried, and then crystallized from ethanol to afford VIa, b.
3-methyl-1-(1,2,3,4-tetrahydroacridin-9-yl)-1H-pyrazol-5-ol (VIa)
Crystallized from ethanol, m.p. 216–218 °C and yield 22 %. IR spectrum (K Br,
cm-1): 3325 (OH), 2957 (C–H of aliphatic), 1675 (C=O of pyrazolone), 1633 and
1
1448.28 (C=C, st, aromatic); H NMR spectrum (DMSO-d6, ppm): 1.8 (mm, 4H,
2CH2), 2.6 (s, 3H, CH3), 2.80 (t, 2H, CH2), 3.3 (t, 2H, CH2), 7.2–8.2 (m, 4H, C–H
aromatic, 1H, –C=H of pyrazolone), 10.1 (s, H, OH exchangeable with D2O); 13C
NMR (DMSO d6): d 18.0, 20.6, 22.6, 22.7, 31.4, 91.4, 114.5, 122.4, 125.7, 127.2,
123

O. A. Fathhalla et al.
127.9, 128.6, 141.8, 144.8, 161.0, 164.5. Analysis for C17H17N3O (279): required:
C, 73.36; H, 5.79; N, 15.10; found: C, 73.55; H, 5.21; N, 15.37.
9-(3,5-dimethyl-1H-pyrazol-1-yl)-1,2,3,4-tetrahydroacridine (VIb)
Crystallized from ethanol to give product of type VIb with m.p. 140–142 °C and yield
11 %. 1H NMR spectrum (DMSO-d6, ppm): 1.8 (mm, 4H, 2CH2), 2.4, 2.6 (s, s, 6H,
2CH3), 2.80 (t, 2H, CH2), 3.3 (t, 2H, CH2), 7.2–8.2 (m, 4H, C–H aromatic, 1H, –C=H
of pyrazole); 13C NMR (DMSO d6): d 22.8, 22.8, 23.1, 31.4, 11.1, 18.0, 105.0, 114.5,
122.4, 125.7, 127.2, 127.9, 128.6, 144.3, 144.8, 145.4, 164.5. Analysis for C18H19N3
(277): required: C, 77.66; H, 7.24; N, 15.09; found: C, 77.28; H, 7.48; N, 15.14.
General method for preparation of compounds VIIa–d
A mixture of 9-hydrazino-1,2,3,4-tetrahydroacridine (2.1 g, 0.1 mol) and the
appropriate trisubstituted vinylcyanide (0.1 mol) in absolute methanol (50 ml)
containing triethylamine (1.5–2 ml) (except VIIb) was heated under reflux for 24 h.
The solvent was evaporated and the precipitate formed was filtered off, dried, and
crystallized from ethanol to give the compounds VIIa–d.
5-amino-3-(methylthio)-1-(1,2,3,4-tetrahydroacridin-9-yl)-1H-pyrazole-
4-carbonitrile (VIIa)
Crystallized from ethanol to give brown powder with m.p. 230–232 °C and yield
60 %. IR spectrum (K Br, cm-1): 3343, 3186 (NH2), 2940 (C–H aliphatic) and 2216
(C:N); 1H NMR spectrum (DMSO-d6, ppm): 1.8 (mm, 4H, 2CH2), 2.4 (s, 3H, –S–
CH3), 2.50 (t, 2H, CH2), 3.3 (t, 2H, CH2), 5.9 (b, 2H, NH2 exchangeable with D2O),
6.8–8.1 (m, 4H, C–H aromatic). Analysis for C18H17N5S (335): required: C, 64.45;
H, 5.11; N, 20.88; found: C, 64.55; H, 5.21; N, 20.68.
5-amino-1-(1,2,3,4-tetrahydroacridin-9-yl)-1H-pyrazole-4-carbonitrile (VIIb)
Crystallized from ethanol to give brown powder with m.p. 260–265 °C and yield 57 %.
IR spectrum (K Br, cm-1): 3385 (NH2), 2209 (C:N), 1632 (C=N); 1H NMR spectrum
(DMSO-d6, ppm): 1.8 (mm, 4H, 2CH2), 2.50 (t, 2H, CH2), 3.3 (t, 2H, CH2), 3.8 (b, 2H,
NH2 exchangeable with D2O), 6.78.04 (m, 5H, C–H aromatic). Analysis for C17H15N5
(289): required: C, 70.57; H, 5.23; N, 24.20; found: C, 70.58; H, 5.13; N, 24.22.
Methyl 5-amino-3-(1,5-dimethyl-3-oxo-2-phenylpyrazolidin-4-ylamino)-1-(1,2,3,4-
tetrahydroacridin-9-yl)-1H-pyrazole-4-carboxylate (VIIc)
Crystallized from ethanol to give yellowish brown powder with m.p. 270–275 °C
and yield 19 %. IR spectrum (K Br, cm-1): 3549 (NH2), 3155, 3099 (C–H of
aromatic), 2936 (C–H of CH3), 1643 (C=O of amide), 1700 (C=O of COOCH3); 1H
NMR spectrum (DMSO-d6, ppm): 2.1 (mm, 4H, 2CH2), 2.25 (t, 2H, CH2), 2.6 (s,
3H, C–CH3), 3.25 (t, 2H, CH2), 3.49 (s, 3H, N–CH3), 3.85 (s, 3H, OCH3), 7.3–7.5
123

Synthesis of certain tetrahydroacridine derivatives
(m, 9H, C–H aromatic), 4.38 (b, 2H, NH2 exchangeable with D2O), 9.7 (s, 1H, NH
exchangeable with D2O). Analysis for C29H29N7O3 (523): required: C, 66.20; H,
5.58; N, 18.80; found: C, 66.18; H, 5.56; N, 18.78.
5-amino-3-(1,5-dimethyl-3-oxo-2-phenylpyrazolidin-4-ylamino)-1-(1,2,3,4-
tetrahydroacridin-9-yl)-1H-pyrazole-4-carbonitrile (VIId)
Crystallized from ethanol to give pale brown powder with m.p. 255–257 °C and
yield 19 %. IR spectrum (K Br, cm-1): 3424 (NH2), 3058, (C–H aromatic), 2924
(C–H of CH3), 2204 (C:N), 1657 (C=O of amide). Analysis for C28H26N8O (490):
required: C, 68.10; H, 5.44; N, 22.84; found: C, 68.08; H, 5.42; N, 33.82.
General method for preparation of 9-(2-{[(4-substituted heterocyclic sulfonyl
chloride)-thio]peroxy}hydrazino)-1,2,3,4-tetrahydroacridine (VIIIa–d)
A mixture of IIIa (2.13 g, 0.1 mol) and the appropriate sulfonyl chloride
[containing a catalytic amount of pyridine (2 ml) in VIId] was dissolved in
30 ml absolute methanol and then refluxed for 18–24 h. The solvent was
evaporated, and the solid product obtained was filtered off, dried on air suction,
and then crystallized from ethanol.
N0-(1,2,3,4-tetrahydroacridin-9-yl)benzenesulfonohydrazide (VIIIa)
Pale yellowish brown powder with m.p. 293–290 °C and yield 45 %. IR spectrum (K Br,
cm-1): 3545 (N–H), 3060 (C–H aromatic), 1212–1175 (SO2). Analysis for C19H19N3O2S
(353): required: C, 64.57; H, 5.42; N, 11.89; found: C, 64.57; H, 5.32; N, 11.99.
4-methyl-N0-(1,2,3,4-tetrahydroacridin-9-yl)benzenesulfonohydrazide (VIIIb)
Brown powder with m.p. 270–272 °C and yield 55 %. IR spectrum (K Br, cm-1):
3431 (N–H), 3064 (C–H aromatic), 1255–1174 (SO2); 1H NMR spectrum (DMSO-
d6, ppm): 1.8 (mm, 4H, 2CH2), 2.50 (t, 2H, CH2), 3.3 (t, 2H, CH2), 2.9 (s, 3H, CH3)
7.4–7.9 (m, 8H, C–H aromatic), 9.4, 9.7 (s, 2H, 2 NH, exchangeable with D2O).
Analysis for C20H21N3O2S (367): required: C, 65.37; H, 5.76; N, 11.44; found: C,
65.33; H, 5.66; N, 11.45.
4-bromo-N0-(1,2,3,4-tetrahydroacridin-9-yl)benzenesulfonohydrazide (VIIIc)
Pale brown powder with m.p. 220–222 °C and yield 51 %. IR spectrum (K Br,
1
cm-1): 3431 (N–H), 3064 (C–H aromatic), 1255–1174 (SO2); H NMR spectrum
(DMSO-d6, ppm): 1.8 (mm, 4H, 2CH2), 2.50 (t, 2H, CH2), 3.3 (t, 2H, CH2), 7.4–7.8
(m, 8H, C–H aromatic). 9.4, 9.7 (s, 2H, 2 NH, exchangeable with D2O); 13C NMR
(DMSO d6): d 20.5, 22.8, 22.9, 31.4, 115.6, 119.5, 119.9, 124.4, 126.3, 128.2,
128.3, 129.5, 129.5, 132.0, 132.0, 138.7, 145.4, 147.6, 164.2. Analysis for
C19H18BrN3O2S (431): required: C, 52.79; H, 4.20; N, 9.82; found: C, 52.78; H,
4.10; N, 9.72.
123

O. A. Fathhalla et al.
4-oxo-N0-(1,2,3,4-tetrahydroacridin-9-yl)-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-
sulfonohydrazide (VIIId)
Pale yellowish powder with m.p. 250–252 °C and yield 40 %. IR spectrum (K Br,
cm-1): 3446, 3292 (NH), 3173, 3109 (C–H aromatic), 1719 (C=O), 1632 (C=N), 1216,
1171 (SO2); 1H NMR spectrum (DMSO-d6, ppm): 1.8 (mm, 4H, 2CH2), 2.50 (t, 2H,
CH2), 2.9 (t, 2H, CH2), 7.3–8.9 (m, 5H, C–H aromatic), 5.6, 11.16, 11.29, 11.47 (m, 4
NH exchangeable with D2O); 13C NMR (DMSO d6): d 20.6, 22.8, 22.9, 31.4, 103,
115.6, 119.5, 119.9, 124.4, 128.2, 128.3, 145.4, 1467.6, 160, 154.2, 178.1. Analysis for
C17H17N5O3S2 (403): required: C, 50.61; H, 4.25; N, 17.36; found: C, 50.51; H, 4.15;
N, 17.26 (Scheme 2).
General method for preparation of 3-(1,2,3,4-tetrahydroacridine)-2(substituted)-
1,3-thiazolidin-4-one (IXa–c)
A mixture of IVa–c (0.1 mol) and thioglycolic acid (0.092 g, 0.1 mol) in dry
benzene (15 ml) was heated in a water bath for 6–10 h. The volatile solvent was
evaporated and the reaction mixture was neutralized with cold dilute sodium
bicarbonate solution. The solid was filtered off, dried under air suction, and then
crystallized from ethanol to give the compounds IXa–c.
HN-N=CHAr
NH-NH-SO2-Z
N
IVa-c
N
VIIIa-d
NHNH2
L
C
VIIIa : Z =
VIIIb : Z=
VIIIc : Z =
CH3
O2
IVa : Ar =
IVb : Ar =
S
-
Z
CH3
Br
OCH3
N
OCH3
X
IIIa
IVc : Ar =
NCS
Y
Z
X
CH3
H
N
OCH3
CN
C
O
VIIId : Z = S
CH2
N
H
Z
S
O
C
R
O
NHNH-C-NH-
N
NH2
N
N
CH3
N
V
N
R
N
N
CH3
NH
H3C
VIIa-d
N
N
X = H, SCH3 ,
,
O
VIa,b
Y
= SCH3 , OC2H5
VIa : R = OH
VIb : R = CH3
,
Z = C O2CH
3 CN
Scheme 2 Structure of compounds IV–VIII
123

Synthesis of certain tetrahydroacridine derivatives
3-(1,2,3,4-tetrahydroacridin-9-ylamino)-2-p-tolylthiazolidin-4-one (IXa)
Crystallized from ethanol to give brown powder with m.p. 210–215 °C and yield
41 %. IR spectrum (K Br, cm-1): 3237 (NH), 2936 (C–H, st, aliphatic), 1713 (C=O);
1H NMR spectrum (DMSO-d6, ppm): 1.85 (mm, 4H, 2CH2), 2.30 (t, 2H, CH2), 2.5 (s,
3H, CH3), 3.3 (t, 2H, CH2), 4.6 (m, 2H, CH2), 4.8 (s, H, CH–N), 7.2–8.2 (m, 8H, C–H
aromatic), 11.88 (s, H, NH exchangeable with D2O). Analysis for C23H23N3OS (391):
required: C, 70.92; H, 5.95; N, 10.79; found: C, 70.72; H, 5.55; N, 10.69.
2-(4-methoxyphenyl)-3-(1,2,3,4-tetrahydroacridin-9-ylamino)thiazolidin-4-one
(IXb)
Crystallized from ethanol to give pale brown powder with m.p. 240–243 °C and yield
52 %. IR spectrum (K Br, cm-1): 3063.37 (NH), 1745 (C=O), 1602 and 1475 (C=C, st,
aromatic); 1H NMR spectrum (DMSO-d6, ppm): 1.80 (4H, m, 2CH2), 2.36 (2H, t, CH2),
3.3 (2H, t, CH2), 3.8 (3H, s, OCH3), 4.6 (2H, m, CH2), 4.9 (H, s, CH–N), 7.3–8.7 (8H, m,
C–H aromatic), 11.3 (s, H, NH exchangeable with D2O). Analysis for C23H23N3O2S
(405): required: C, 68.12; H, 5.72; N, 10.36; found: C, 68.22; H, 5.22; N, 10.26.
2-(3,5-dimethoxyphenyl)-3-(1,2,3,4-tetrahydroacridin-9-ylamino)thiazolidin-4-one
(IXc)
Crystallized from ethanol to give pale yellow powder with m.p. 165–166 °C and yield
41 %. IR spectrum (K Br, cm-1): 3418 (NH), 1711 (C=O), 2916 (C–H, st, aromatic),
1455.99 and 1634 (C=C aromatic); 1H NMR spectrum (DMSO-d6, ppm): 1.89 (4H, m,
2CH2), 2.5 (2H, t, CH2), 3.37 (2H, t, CH2), 3.81, 3.83 (6H, s, 2OCH3), 4.5 (2H, m,
CH2), 4.9 (H, s, CH–N), 6.6–8.2 (7H, m, C–H aromatic), 9.3 (H, s, CH–N), 11.4
(H, s, NH exchangeable with D2O); 13C NMR (DMSO d6): d 14.6, 20.4, 22.6, 22.7,
31.4, 36.0, 55.8, 55.9, 58.0. 98.8, 105.1, 105.2, 115.6, 119.5, 119.9, 124.4, 128.2,
128.3, 141.2, 145.4, 161.6, 161.7, 164.2, 168.8. Analysis for C24H25N3O3S (436):
required: C, 66.19; H, 5.79; N, 9.65; found: C, 66.29; H, 5.69; N, 9.45.
Method for preparation of 3-[1,2,3,4-tetrahydroacridin-9-ylimino]-2-(4-
methylphenyl)-5-(morpholin-4-ylmethyl)-1,3-thiazolidin-4-one (X)
A mixture of paraformaldehyde (0.5 g, 0.005 mol) and 15 ml of morpholine in
25 ml absolute ethanol was refluxed for half an hour till complete solubility of the
paraformaldehyde. Compound IXa (2.5 g, 0.02 mol) in 30 ml of ethanol was
warmed and then added to the reaction mixture. The whole mixture was refluxed for
12 h and left at room temperature for 3 days. Then, the volatile material was
evaporated. The dry residue was extracted with chloroform and crystallized from
methanol to give compound X with m.p. 245–147 °C and yield 65 %. IR spectrum
(K Br, cm-1): 3373 (NH), 1749 (C=O), 2927 (C–H, st, aromatic); 1H NMR
spectrum (DMSO-d6, ppm): 1.85 (4H, m, 2CH2), 2.30 (2H, t, CH2), 2.4 (4H, m,
CH2–N–CH2), 2.5 (3H, s, C–CH3), 3.3 (2H, t, CH2), 3.7 (4H, m, CH2–O–CH2), 4.6
(2H, d, CH2), 7.2–8.6 (8H, m, C–H aromatic, 1H, C–H, of thiazole) 9.2 (H, s, NH,
123

O. A. Fathhalla et al.
exchangeable with D2O). Analysis for C28H32N4O2S (488.65): required: C, 68.82;
H, 6.60; N, 11.47; found: C, 68.80; H, 6.58; N, 11.45.
Method for preparation of 2-(3,5-dimethoxybenzyl)-3-(1,2,3,4-
tetrahydroacridin-9-amino)-7-(2,5-dimethoxybenzyl)-5-amino-6-cyano-3H-
thienol (XI)
To a mixture of IXc (1.5 g, 0.1 mol) and 2,5-dimethoxybenzylidene malononitrile
(0.7 g, 0.1 mol) in 30 ml methanol was added three drops of pyridine to turn it
alkaline. Then, it was refluxed for 24 h. After cooling, the formed solid was filtered
off, dried under air suction, and then crystallized from ethanol to give product XI
with m.p. 295–297 °C and yield 55 %. IR spectrum (K Br, cm-1): 3424, 3123
(NH2), 2293 (C–H st, aromatic), 2183.8 (CN); 1H NMR spectrum (DMSO-d6,
ppm): 1.85 (4H, m, 2CH2), 2.30 (2H, t, CH2), 2.5 (3H, s, C–CH3), 3.3 (2H, t, CH2),
3.6, 3.7, 3.8, 3.9 (12H, s, 4OCH3), 7.1–8.9 (10H, m, C–H aromatic, C–H of
pyrane, C–H of thiazole), 5.2–6.1, 10.6 (3H, b, NH, NH2 exchangeable with D2O).
Analysis for C36H35N5O5S (649): required: C, 66.55; H, 5.43; N, 10.78; found: C,
67.41; H, 6.38; N, 10.08 (Scheme 3).
O
N
CH2
S
O
N
H3C
NH
S
HN-N=CHAr
(IXa)
N
X
Ar
O
N
HS-CH2-COOH
NH
N
IVa-c
N
CH3
IVa : Ar =
IVb : Ar =
(IXc)
IXa-c
OCH3
CH
OCH3
OCH3
H3CO
CH3
IXa : Ar =
IXb : Ar =
C
CN
OCH3
OCH3
IVc : Ar =
CN
OCH3
OCH3
H3CO
IXc : Ar =
H
CN
OCH3
H3CO
S
NH2
O
N
NH
H3CO
N
XI
Scheme 3 Structure of compounds IX–XI
123

Synthesis of certain tetrahydroacridine derivatives
General method for preparation 1-(1,2,3,4-tetrahydroacridin-9-yl)-3-methylthio-
4-cyano5-arylidiniminopyrazole (XIIa–c)
A mixture of VIIa (3.3 g, 1 mol) and the appropriate aldehyde (0.1 mol), namely,
4-methoxybenzaldehyde, 4-chlorobenzaldehyde, and 4-nitrobenzaldehyde, in 50 ml
absolute ethanol was refluxed for 18–24 h. After cooling, the produced precipitate
was filtered off, dried under air suction, and then crystallized from the proper
solvent to give compounds XIIa–c.
(E)-5-(4-methoxybenzylideneamino)-3-(methylthio)-1-(1,2,3,4-tetrahydroacridin-9-
yl )-1H-pyrazole-4-carbonitrile (XIIa)
Crystallized from proper solvent to give yellowish brown powder with m.p.
200–207 °C and yield 58 %. IR spectrum (K Br, cm-1): 3121.22, 3066.26 (C–H
aromatic), 2214 (CN), 1633.41 (C=N); H NMR spectrum (DMSO-d6, ppm): 1.85
1
(mm, 4H, 2CH2), 2.4 (t, 2H, CH2), 2.5 (s, 3H, S–CH3), 3.5 (t, 2H, CH2), 3.8 (s, 3H,
OCH3), 8.1 (s, H, CH=N), 7.2–7.9 (m, 8H, C–H aromatic). Analysis for
C26H23N5OS (453): required: C, 68.85; H, 5.11; N, 15.44; found: C, 68.95; H,
5.21; N, 15.74.
(E)-5-(4-chlorobenzylideneamino)-3-(methylthio)-1-(1,2,3,4-tetrahydroacridin-9-
yl)-1H-pyrazole-4-carbonitrile (XIIb)
Crystallized from proper solvent to give brown powder with m.p. 270–275 °C and
yield 54 %. IR spectrum (K Br, cm-1): 3346, 3005 (C–H aromatic), 2212.9
1
(CN), 1653 (C=N), 1107 (C–Cl); H NMR spectrum (DMSO-d6, ppm): 1.82 (mm,
4H, 2CH2), 2.6 (t, 2H, CH2), 2.8 (s, 3H, S–CH3), 3.8 (t, 2H, CH2), 8.3 (s, H,
CH = N), 7.4–9.1 (m, 8H, C–H aromatic). Analysis for C25H20ClN5S (457):
required: C, 65.57; H, 4.40; N, 15.29; found: C, 65.55; H, 4.38; N, 15.27.
(E)-3-(methylthio)-5-(4-nitrobenzylideneamino)-1-(1,2,3,4-tetrahydroacridin-9-yl)-
1H-pyrazole-4-carbonitrile (XIIc)
Pale brown powder with m.p. 250–255 °C and yield 52 %. IR spectrum (K Br,
cm-1): 3239, 3080 (C–H aromatic), 2214 (CN), 1632 (C=N), 1330 (NO2, st,
1
symmetric); H NMR spectrum (DMSO-d6, ppm): 1.85 (4H, m, 2CH2), 2.5 (2H, t,
CH2), 2.6 (3H, s, S–CH3), 3.3 (2H, t, CH2), 7.9 (H, s, CH = N), 7.7–8.7 (8H, m,
C–H aromatic). Analysis for C25H20N6O2S (468): required: C, 64.09; H, 4.30; N,
17.94; found: C, 64.19; H, 4.40; N, 17.74.
General method for preparation of ( )1-(1,2,3,4-tetrahydroacridin-9-yl)-3-
methylthio-4-cyano-5-(2-aryl-1,3-thiazolidine-4-oxo-3-yl)pyrazole (XIIIa–c)
A mixture of XIIa–c (0.1 mol) and thioglycolic acid (0.092 g, 0.1 mol) in dry
benzene (15 ml) was heating in a water bath for 6–10 h. The volatile solvent was
evaporated and the reaction mixture was neutralized with cold dilute sodium
123

O. A. Fathhalla et al.
bicarbonate solution. The solid obtained was filtered off, dried under air suction, and
then crystallized from ethanol.
5-(4-(4-methoxyphenyl)-2-oxothiazolidin-3-yl)-3-(methylthio)-1-(1,2,3,4-
tetrahydroacridin-9-yl)-1H-pyrazole-4-carbonitrile (XIIIa)
Brown powder with m.p. 285–287 °C and yield 47 %. IR spectrum (K Br, cm-1):
1
3181 (C–H aromatic), 2214 (C:N), 1644 (C=O); H NMR spectrum (DMSO-d6,
ppm): 1.85 (mm, 4H, 2CH2), 2.4 (t, 2H, CH2), 2.5 (s, 3H, S–CH3), 3.5 (t, 2H, CH2),
3.8 (s, 3H, OCH3), 4.0 (s, H, CH–N), 4.9 (m, 2H, CH2), 7.2–7.9 (m, 8H, C–H
aromatic). Analysis for C28H25N5O2S2 (527): required: C, 63.74; H, 4.78; N, 13.27;
found: C, 63.64; H, 4.58; N, 13.07.
5-(4-(4-chlorophenyl)-2-oxothiazolidin-3-yl)-3-(methylthio)-1-(1,2,3,4-
tetrahydroacridin-9-yl)-1H-pyrazole-4-carbonitrile (XIIIb)
Pale brown powder with m.p. 270–276 °C and yield 51 %. IR spectrum (K Br,
cm-1): 3030 (C–H aromatic), 2200 (C:N), 1654 (C=O); 1H NMR spectrum
(DMSO-d6, ppm): 1.82 (mm, 4H, 2CH2), 2.6 (t, 2H, CH2), 2.8 (s, 3H, S–CH3), 3.8
(t, 2H, CH2), 4.3 (s, H, CH–N), 4.6 (m, 2H, CH2), 7.4–9.1 (m, 8H, C–H aromatic).
Analysis for C27H22ClN5OS2 (532): required: C, 60.95; H, 4.17; N, 13.16; found:
C, 60.93; H, 4.15; N, 13.14.
3-(methylthio)-5-(4-(4-nitrophenyl)-2-oxothiazolidin-3-yl)-1-(1,2,3,4-
tetrahydroacridin-9-yl)-1H-pyrazole-4-carbonitrile (XIIIc)
Brown crystals with m.p. 294–295 °C and yield 24 %. IR spectrum (K Br, cm-1):
1
3169 (C–H aromatic), 2220 (C:N), 1646 (C=O); H NMR spectrum (DMSO-d6,
ppm): 1.88 (mm, 4H, 2CH2), 2.5 (t, 2H, CH2), 2.6 (s, 3H, S–CH3), 3.2 (t, 2H, CH2),
4.2 (s, H, CH–N), 4.8 (m, 2H, CH2), 7.1–8.2 (m, 8H, C–H aromatic). Analysis for
C27H22N6O3S2 (542): required: C, 59.76; H, 4.09; N, 15.49; found: C, 59.56;
H, 4.19; N, 15.29.
Method for preparation of 3-(methylthio)-1-(1,2,3,4-tetrahydroacridin-9-yl)-1,5-
dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one (XIV)
A mixture of VIIa (3.3 g 1 mol) and 33 ml formic acid was refluxed for 24 h. Then
ice water was poured into the mixture, its pH adjusted to 6 by using NaOH, and the
produced precipitate was filtered off, dried under air suction, and then crystallized
from ethanol.
Yellowish brown powder with m.p. 278–280 °C and yield 80 %. IR spectrum (K
Br, cm-1): 3395 (NH), 2936 (C–H aliphatic), 2813 (C–H of CH3), 1650 (C=O); 1H
NMR spectrum (DMSO-d6, ppm): 1.9 (mm, 4H, 2CH2), 2.4 (s, 3H, –S–CH3), 2.50
(t, 2H, CH2), 3.1 (t, 2H, CH2), 6.3 (s, 1H, C–H of pyrimidine), 6.8–8.1 (m, 4H, C–H
aromatic), 5.2 (s, 1H, NH, exchangeable with D2O). Analysis for C19H17N5OS
(363): required: C, 62.79; H, 4.71; N, 19.27; found: C, 62.59; H, 4.71; N, 19.27.
123

Synthesis of certain tetrahydroacridine derivatives
Method for preparation of 9-[4-chloro-3-(methylthio)-4,5-dihydro-1H-
pyrazolo[3,4-d]pyrimidin-1-yl]-1,2,3,4-tetrahydroacridine (XV)
A mixture of XIV (3.6 g, 1 mol) and 20 ml phosphoryloxychloride was heated in a
sand bath at 80 °C for 7 h. After cooling, ice water was poured into the mixture with
stirring and it was left to stand for 5 h to precipitate. The produced precipitate was
filtered off, dried under suction, and then crystallized from ethanol.
Brown powder with m.p. 270–275 °C and yield 55 %. IR spectrum (K Br, cm-1):
1
3076 (C–H aromatic), 2936 (C–H of CH3); H NMR spectrum (DMSO-d6, ppm):
1.8 (mm, 4H, 2CH2), 2.4 (s, 3H, –S–CH3), 2.50 (t, 2H, CH2), 3.2 (t, 2H, CH2), 7.8
(s, 1H, C–H of pyrimidine), 6.4–8.2 (m, 4H, C–H aromatic). Analysis for
C19H16ClN5S (381.5): required: C, 59.45; H, 4.73; N, 18.24; found: C, 59.55; H,
4.53; N, 18.14.
Method for preparation of 9-[9-(methylthio)-7H-pyrazolo[4,3-e]tetrazolo[1,5-
c]pyrimidin-7-yl]-1,2,3,4-tetrahydroacridine (XVI)
A mixture of XV (3.6 g, 1 mol) and sodium azide (0.7 g, 0.1 mol) in 15 ml glacial
acetic acid was refluxed for 24 h. After cooling, the produced precipitate was
filtered off, dried under suction, and then crystallized from ethanol.
Dark brown powder with m.p. 255–257 °C and yield 15 %. IR spectrum (K Br,
cm-1): 3078 (C–H aromatic), 2985 (C–H of CH3), 1624 (C=N); 1H NMR spectrum
(DMSO-d6, ppm): 1.8 (mm, 4H, 2CH2), 2.4 (s, 3H, –S–CH3), 2.50 (t, 2H, CH2), 3.2
(t, 2H, CH2), 8.1 (s, 1H, C–H of pyrimidine), 7.4–8.4 (m, 4H, C–H aromatic).
Analysis for C19H16N8S (388): required: C, 58.75; H, 4.15; N, 28.85; found: C,
58.55; H, 4.25; N, 28.65.
Method for preparation of 1,5-dimethyl-4-{[3-(methylthio)-1(1,2,3,4-
tetrahydroacridine)-pyrazolo[3,4-d]pyrimidin-4-yl]amino}-2-phenyl-1,2-
dihydro-3H-pyrazol-3-one (XVII)
A mixture of XV (3.6 g, 1 mol) and 4-aminoantipyrine (2.8 g) with 0.5 ml of
pyridine in 20 ml absolute methanol was refluxed for 24 h. The produced precipitate
was filtered off, dried under suction, and then crystallized from ethanol.
Yellow crystal with m.p. 295–297 °C and yield 79 %. 1H NMR spectrum
(DMSO-d6, ppm): 1.8 (mm, 4H, 2CH2), 2.4 (s, 3H, C–CH3), 2.45 (s, 3H, –S–CH3),
2.50 (t, 2H, CH2), 3.2 (t, 2H, CH2), 3.7 (s, 3H, N–CH3), 7.4–8.4 (m, 9H, C–H
aromatic, s, 1H of pyrimidine), 10.5 (s, 1H, NH exchangeable with D2O). Analysis
for C30H28N8OS (548): required: C, 65.43; H, 5.49; N, 20.35; found: C, 65.67; H,
5.14; N, 20.42.
General method for preparation of compounds XVIIIa, b)
A mixture of XV (0.1 mol) and anthranilic acid (1 g, 0.1 mol) in n-butanol (20 ml)
in case of compound XVIIIa and in methanol (20 ml) with 2 ml of pyridine in case
123

O. A. Fathhalla et al.
of compound XVIIIa was refluxed for 24 h. The produced precipitate was filtered
off, dried, and crystallized from methanol.
8-[(1,2,3,4-tetrahydroacridin-9-yl)-1-methylsulfanyl-3H-2,3,4,5a,11-pentaaza-
cyclopena[a]anthracen-6-one (XVIIIa)
Pale brown powder with m.p. 290–292 °C and yield 41 %. IR spectrum (K Br,
1
cm-1): 3407 (C–H aromatic), 2935 (C–H of CH3), 1720 (C=O), 1632 (C=N); H
NMR spectrum (DMSO-d6, ppm): 1.8 (mm, 4H, 2CH2), 2.4 (s, 3H, –S–CH3), 2.50
(t, 2H, CH2), 3.2 (t, 2H, CH2), 7.6–8.2 (m, 8H, C–H aromatic), 8.9 (s, 1H, CH of
pyrimidine); 13C NMR (DMSO d6): d 20.5, 22.8, 22.9, 23.2, 31.4, 105, 114.5,
120.9, 122.4, 122.5, 125.7, 128.6, 128.8, 133, 144.8, 145.4, 147.1, 148.9, 163,
164.5, 170.6. Analysis for C24H20N6 (390): required: C, 73.83; H, 4.65; N, 21.52;
found: C, 73.73; H, 4.55; N, 21.32.
2-(3-(methylthio)-1-(1,2,3,4-tetrahydroacridin-9-yl)-1H-pyrazolo[3,4-d]pyrimidin-
4-ylamino)benzoic acid (XVIIIb)
Dark pale brown powder with m.p. 274–272 °C and yield 39 %. IR spectrum (K Br,
1
cm-1): 3739 (O–H), 3390.24 (C–H aromatic), 1720 (C=O), 1632.45 (C=N); H
NMR spectrum (DMSO-d6, ppm): 1.8 (mm, 4H, 2CH2), 2.0 (s, 1H, NH
exchangeable with D2O), 2.4 (s, 3H, –S–CH3), 2.50 (t, 2H, CH2), 3.2 (t, 2H,
CH2), 7.5–8.1 (m, 8H, C–H aromatic), 8.4 (s, 1H, CH of pyrimidine), 10.5 (s, 1H,
OH exchangeable with D2O); 13C NMR (DMSO d6): d 14.6, 20.6, 22.8, 22.9, 31.4,
105, 114.5, 116.4, 122.2, 122.4, 125.7, 127.2, 127.3, 127.9, 128.6, 131.6, 133,
135.3, 144.5, 144.8, 145.4, 148.9, 149.9, 159.0, 159.9, 164.5, 169.4. Analysis for
C26H22N6O2S (482): required: C, 64.61; H, 4.60; N, 17.42; found: C, 64.51; H, 4.20;
N, 17.22 (Scheme 4).
Results and discussion
The synthesis of 10H-1,2,3,4-tetrahydroacridin-9-one I and, particularly, the
unsubstituted derivative (R = H) has been carried out by two methods (Fig. 1).
Method A (isolating or not the intermediate Schiff base) was discovered by Tiedtke
[30] and improved by Reed [31] and Albert [32]. The yields are 40 % (R = H) and
77 % (R = 2-Me) [31–35]. Method B (isolating or not the anil intermediate) was
discovered by Sen and Basu [36, 37] and improved by Hughes and Lions [38].
The yield on I (R = H) varies between 20 and 90 % [36], but one must consider
that acridones are high melting, very insoluble compounds and difficult to purify.
9-Chlorotetrahydroacridines have been prepared by the reaction of the correspond-
ing 10H tetrahydroacridin-9-ones with phosphorus oxychloride [31–33]. It has been
reported [39] that four 9-substituted amino-1,2,3,4-tetrahydroacridines have the
general formula of compounds IIIa, b, which have been prepared via transformation
of the respective 9-chlorotetrahydroacridines. The nucleophilic substitution of the
chlorine atom in compound II is difficult.
123

Synthesis of certain tetrahydroacridine derivatives
H3CS
N
CN
NH2
N
N
Formic acid
RCHO
O
VIIa
H3CS
NH
CN
Ar
H3CS
H3CS
CN
N
N
N
N
N
N
S
N
N
N
N CH Ar
HS
N
CH2 COOH
O
XIV
N
OCH3
a, Ar =
XIIIa-c
POCL3
XIIa-c
Cl
b, Ar =
c,Ar =
NO2
Cl
H
N
SCH3
N
N
N
Anthranilic acid
NaN3
N
XV
N
CH3
CH3
N
N
N
N
SCH3
HN
N
O
COOH
N
NH
N
N
SCH3
N
NH
H3CS
N
N
H3CS
N
N
O
N
N
N
N
N
N
N
N
N
N
N
XVI
XVIIIa
XVII
XVIIIb
Scheme 4 Structure of compounds XII–XVIII
Compounds IVa–c were prepared in a good yield by the condensation of IIIa
with the appropriate aldehyde in absolute ethanol. The precipitate was dried and
then crystallized from ethanol to give the title compounds, whose chemical
structures were confirmed by microanalytical and spectral data.
Compound V was prepared by the condensation of IIIa and cyclohexyl
isothiocyanate in the least amount in ethyl alcohol. Compounds VIa, b were prepared
by the condensation of IIIa and the appropriate 1,3-dicarbonyl compound (ethylace-
toacetate, acetyl acetone) in absolute ethanol to give a good yield. Compounds VIIa–d
123

O. A. Fathhalla et al.
COOH
NH2
Cu
+
O
X
COOH
cyclyzation
X = halogen
NH
NH
acredone
Cu
2-carboxy-diphenylamine
COOH
X
+
reduction
H2N
oxidation
Cyclization: POCl3; H2SO4; PPA, etc...,
Reduction: Na, BuOH, !, etc...,
N
NH
Oxidation: CrO3; NaOH aq.; FeCl3; HNO3, etc
acridine
acredane
Fig. 1
were prepared by the condensation of IIIa and the appropriate trisubstituted
vinylcyanide to give the title compounds VIIa–d. Compounds VIIIa–d were
prepared by refluxing IIIa and the appropriate heterocyclic sulfonyl chloride (with
pyridine in VIIId) in absolute methanol to give the corresponding compound. The
series of compounds IXa–c was prepared by the condensation of IVa–c with
thioglycolic acid in dry benzene and then neutralizing with sodium bicarbonate
solution. The condensation of paraformaldehyde and morpholine in absolute ethanol
was progressed till complete solubility of paraformaldehyde and then compound IXa
was added, which was dissolved in ethanol after heating the reaction mixture and then
refluxed to give compound X. The compound IXc was condensed with 2,5-
dimethoxybenzylidene malononitrile in methanol and pyridine to give product XI.
Compounds XIIa–c were prepared by the condensation of VIIa and the appropriate
aldehyde in absolute ethanol to give the compounds XIIa–c. Compounds XIIIa–c
were achieved by the mixture of XIIa–c and thioglycolic acid in dry benzene to give
XIIIa–c. Compound XIV was prepared by the condensation of VIIa with formic acid
(3.3 ml). The pH was adjusted to 6 by using dilute NaOH to give compound XIV.
Compound XV was prepared by the condensation of XIV and phosphoryloxychloride,
which was then poured into ice water with stirring to give compound XV. Compound
XVI was prepared by the mixture of XV and sodium azide in glacial acetic acid, which
was refluxed to give compound XVI. Compound XVII was prepared by the
condensation of XV and 4-aminoantipyrine with pyridine in absolute methanol.
Compound XVIIIa was prepared by the condensation of XV and anthranilic acid in
n-butanol. Compound XVIIIb was prepared by the condensation of XV and
anthranilic acid with pyridine in methanol and crystallized from ethanol.
Pharmacology
Antitumor activity
In vitro tests were performed for the new compounds’ cytotoxic effects [1–4].
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Synthesis of certain tetrahydroacridine derivatives
Experiment
Measurement of potential cytotoxicity by SRB assay
The eight tetrahydroacridine derivatives (compounds I–VIII) were subjected to a
screening system for the evaluation of their antitumor activity against the liver
cancer (HEPG2) tumor cell line in comparison to the known anticancer drugs,
5-fluorouracil and doxorubicin.
The potential cytotoxicity of the selected tetrahydroacridine derivatives was
tested using the method of Skehan et al. [40] as follows:
1. Cells were plated in 96-well plates (104 cells/well) for 24 h before treatment
with the compound(s) to allow attachment of cells to the walls of the plate.
2. Different concentrations of the compound under test (0, 1, 2.5, 5, 10 lg/ml)
were added to the cell monolayer. Triplicate wells were prepared for each
individual dose.
3. Monolayer cells were incubated with the compound(s) for 48 h at 37 °C and in
an atmosphere of 5 % CO2.
4. After 48 h, the cells were fixed, washed, and stained with sulforhodamine B
stain.
5. Excess stain was washed with acetic acid and attached stain was recovered with
Tris-EDTA buffer.
6. Color intensity was measured using an ELISA reader.
7. The relation between surviving fraction and drug concentration is plotted in
order to obtain the survival curve of each tumor cell line treatment with the
specified compound.
Biochemical analysis
The biochemical effects of the selected tetrahydroacridine derivatives (eight
compounds) on some enzymes such as aspartate and alanine aminotransferases
(AST and ALT), alkaline phosphatase (ALP), total protein content, albumin,
globulins, creatinine, total lipids, cholesterol, triglycerides, and bilirubin in the
serum of mice were evaluated in comparison to 5-fluorouracil and doxorubicin.
Different biochemical parameters were realized in control and treated mice
groups as follows:
1. Estimation of ALT, AST, and ALP activity levels were done using a blood
autoanalyzer (Olympus AU400, Japan)
2. Total proteins, albumin, globulins, and creatinine in the serum of mice were
estimated according to the technique described by Faddah and Soliman [41]
3. Total lipids, cholesterol, triglycerides, and bilirubin in the serum of mice were
estimated according to the technique described by Soliman and Faddah [42]
Statistical analysis of the results was performed using Chi-square values (SPSS
software package).
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O. A. Fathhalla et al.
Table 1 Effect of some
selected tetrahydroacridine
derivatives on the hepatic
carcinoma cell line HEPG2
Compounds
IC50
Doxorubicin (Dox)
3.56 lg/ml
5 lg/ml
5-Fluorouracil (5-FU)
VIIa
VIIIc
IVa
18 lg/ml
19.1 lg/ml
24.6 lg/ml
0.694 lg/ml
2.97 lg/ml
14.9 lg/ml
21.1 lg/ml
18.5 lg/ml
VIb
XVIIIa
VIIId
VIIb
IIIb
Results
Many tetrahydroacridine derivatives have been synthesized in order to evaluate their
antitumor activities as a trial to obtain more effective and less toxic agents. The
antitumor activity results indicated that the selected tetrahydroacridine derivatives
showed antitumor activity against the liver cancer (HEPG2) tumor cell line tested,
but with varying intensities in comparison to the known anticancer drugs
5-fluorouracil and doxorubicin.
Table 1 shows that all compounds exhibited a moderate growth inhibition
activity on the tested tumor panel cell line in 1–10 lg/ml concentrations in
comparison to the known anticancer drugs 5-fluorouracil and doxorubicin.
It was found that compound VIb was the most active and induced a marked
growth inhibition (0.694 lg/ml concentration) in a dose-dependent manner against
liver cancer (HEPG2), while compound XVIIIa was second in regards to the growth
inhibition activity (2.97 lg/ml concentration). The rest of the compounds,
VIIa,VIIIc, IVa, VIIId, VIIb, and IIIb, exhibited less inhibition activities, with
concentrations of 18, 19.1, 24.6, 14.9, 21.1, and 18.5 lg/ml.
It is noticed from the results that the novel derivatives induced a significant
growth inhibition towards the liver cancer (HEPG2) cell line in comparison to
5-fluorouracil and doxorubicin after treatment with IC50 values (ranging from
0.694 to 2.97 lg/ml concentrations) for compounds VIb and XVIIIa, while the
IC50 values for 5-fluorouracil was 5 lg/ml concentration and doxorubicin was
3.56 lg/ml concentration.
Acknowledgments The authors are grateful to the members of the Therapeutical Chemistry
Department, Pharmaceutical and Drug Industries Division, National Research Centre, for helping to
accomplish this work.
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